1. Technical Field
The present invention relates to a semiconductor memory apparatus, and in particular, to a data conversion circuit of a semiconductor memory apparatus, a semiconductor memory apparatus using the same, and a data conversions method.
2. Related Art
Generally, a semiconductor memory apparatus receives serial data through a single input path. The semiconductor memory apparatus internally converts serial data to parallel data and stores the converted parallel data in memory cells. When the stored data is output, parallel data is converted to serial data. Accordingly, in order to input data to and store data in the semiconductor memory apparatus, an apparatus that converts serial data to parallel data is required. Further, in order to output data from the semiconductor memory apparatus, an apparatus that converts parallel data to serial data is required. That is, the semiconductor memory apparatus requires two circuits, one that converts serial data to parallel data, and one that converts parallel data to serial data.
As shown in FIG. 1, in a general DDR2 SDRAM, a 4-bit pre-fetch method is used in which data is converted by 4 bits at a time.
During a write operation, the semiconductor memory apparatus receives serial data 4-bit Serial Data from an input/output pad 60. The serial data 4-bit Serial Data is converted to parallel data 4-bit Parallel Data by a serial-to-parallel data conversion unit 50, and then the parallel data is transmitted to first to fourth input/output lines GIO_Q<0:3>.
Meanwhile, during a read operation, parallel data 4-bit Parallel Data that is transmitted through the first to fourth input/output lines GIO_Q<0:3> is converted to serial data 4-bit Serial Data by a parallel-to-serial data conversion unit 20, and then the serial data is transmitted to an output driver 30.
As such, in the general semiconductor memory apparatus, the serial-to-parallel data conversion unit 50 and the parallel-to-serial data conversion unit 20 are used to transmit and receive internal data and external data of the semiconductor memory apparatus.
However, since the conventional semiconductor memory apparatus includes a data conversion circuit that converts serial data to parallel data, and a data conversion circuit that converts parallel data to serial data, each circuit occupies a predetermined area. This results in a decrease in integration of the semiconductor memory apparatus.